KR20080072560A - Thermal diffusion sheet and method for positioning thermal diffusion sheet - Google Patents

Abstract

A thermal diffusion sheet and a position deciding method of the thermal diffusion sheet are provided to determine the position of the thermal diffusion sheet for a heating element easily by engaging a position deciding unit with a structure disposed near the heating element. A thermal diffusion sheet(10) is composed of: a graphite sheet(11) for diffusing heat generated from a heating element; a polymer film(12) formed on the graphite sheet; and position deciding units(21,22) for determining the position for the heating element. Upper and lower adhesive layers(14,15) are formed on the upper and under sides of the graphite sheet. The polymer film is adhered to the graphite sheet by the upper adhesive layer. The thermal diffusion sheet is bonded to the heating element by the lower adhesive layer.

Description

Thermal diffusion sheet and thermal diffusion sheet positioning method {THERMAL DIFFUSION SHEET AND METHOD FOR POSITIONING THERMAL DIFFUSION SHEET}

The present invention relates to a heat diffusion sheet for diffusing heat generated from heat generating elements such as electronic components.

With the recent increase in computer performance, the power consumption and heat generation of electronic components such as central processing units (ICs) and integrated circuits (ICs) are increasing. Since the processing capability of the electronic component is lowered by heat, it is necessary to prevent the temperature rise due to the heat of the electronic component. In this regard, it is known to interpose a thermal diffusion sheet such as, for example, a graphite sheet (graphite sheet) between the electronic component and the housing. Graphite sheets have anisotropic thermal conductivity, so the thermal conductivity in a direction parallel to the surface, that is, in the plane direction, is much higher than the thickness direction. For this reason, by interposing a graphite sheet between the electronic component and the housing, heat dissipation can be carried out while diffusing heat generated from the electronic component, thereby degrading the performance of the electronic component due to the temperature rise.

For example, Japanese Laid-Open Patent Publication (Japanese Patent Laid-Open No. 11-087959) discloses a heat dissipation device having a collector as a heat collecting means, a flexible heat conducting device derived from a collector, and a heat pipe as a heat transfer means. In the case of this heat radiating apparatus, the flexible heat conductive apparatus is formed by laminating a plastic sheet on a graphite sheet. Japanese Laid-Open Patent Publication (JP-A-2000-081143) discloses a packing material made of a laminate in which graphite films and plastic films are alternately laminated. Japanese Laid-Open Patent Publication (JP-A 2002-012485) discloses a method of coating an epoxy resin on both surfaces of a graphite sheet.

By the way, in a manufacturing process, such as an electronic device, the said thermal-diffusion sheet | seat can be stuck to electronic components, such as CPU and IC, by manual labor or a machine. Since such electronic components are very small, it is very difficult to accurately attach the thermal diffusion sheet to a predetermined position. In addition, when the thermal diffusion sheet is not adhered correctly, heat generated from the electronic component may not be effectively radiated, which may cause performance deterioration of the electronic component due to temperature rise. For this reason, there is a strong demand for a thermal diffusion sheet capable of easily and accurately positioning a heating element such as an electronic component.

An object of the present invention is to provide a thermal diffusion sheet that can easily and accurately position a heating element such as an electronic component.

In order to achieve the above object, the invention described in claim 1 includes a thermal diffusion sheet having a graphite sheet for diffusing heat generated from a heating element and a polymer film provided on the graphite sheet, and a positioning unit for positioning the heating element. It is a thermal diffusion sheet characterized by having.

According to the said structure, the structure arrange | positioned in the vicinity of a heat generating body is engaged with a positioning part, and positioning of a thermal-diffusion sheet with respect to a heat generating body can be performed easily and reliably. In the invention described in claim 2, the upper and lower adhesive layers are respectively provided on the surface and the lower surface of the graphite sheet, and the polymer film is adhered to the graphite sheet by the upper adhesive layer. And the thermal diffusion sheet is adhered to the heating element by the lower adhesive layer.

According to the said structure, since both surfaces of a graphite sheet are covered by the adhesion layer, the graphite powder peeled from a graphite sheet can be prevented from scattering. In the invention according to claim 3, in the invention according to claim 1 or 2, the positioning portion is a hole that penetrates the polymer film and the upper and lower adhesive layers, and is positioned in the structure of the protrusion arranged on the substrate on which the heating element is mounted. The addition is characterized in that the engagement.

According to the said structure, since a graphite sheet is not exposed in a positioning part, it can further prevent that the graphite powder peeled from a graphite sheet scatters. According to the invention described in claim 4, the heat conductive rubber is additionally provided on the graphite sheet, and the polymer film is provided with a hole for arranging the heat conductive rubber.

According to the above configuration, the thermally conductive rubber is disposed directly on the graphite sheet through the holes of the polymer film. For this reason, the heat diffused from the heating element to the graphite sheet can be radiated to the outside through the thermally conductive rubber. Thereby, since heat dissipation can be efficiently carried out while diffusing heat generated from the heat generating element, a rise in temperature due to heat generated by the heat generating element can be suppressed.

The invention described in claim 5 is characterized in that, in the invention described in claims 1 to 4, the positioning portion is engaged with the structure disposed in the vicinity of the heating element, and the thermal diffusion sheet is positioned with respect to the heating element.

According to the above structure, the positioning portion is engaged with the structure disposed in the vicinity of the heating element, so that the positioning of the thermal diffusion sheet relative to the heating element can be performed easily and reliably.

According to the present invention, positioning with respect to a heating element such as an electronic component can be easily and surely performed.

One embodiment which actualized the thermal-diffusion sheet of this invention is described with reference to FIGS. As shown in FIGS. 1 and 2, the thermal diffusion sheet 10 includes a graphite sheet 11, a polymer film 12 provided on the graphite sheet 11, and a thermally conductive rubber 13. The thermal diffusion sheet 10 is attached to an electronic component that is a heating element, and is used to suppress a temperature rise due to heat generated from the electronic component.

As shown in Fig. 1, the graphite sheet 11 is provided with a notch 11a that forms a right angle at a corner of the left side. A square square hole 11b is provided in the graphite sheet 11 near the corner on the opposite side to the notch 11a, that is, near the right edge.

Both surfaces of the graphite sheet 11, the outer frame, the notches 11a and the inside of the square hole 11b are covered with an adhesive. The pressure-sensitive adhesive is applied in a thin and almost uniform thickness on each side of the graphite sheet 11. For this reason, the 1st adhesion layer 14 as an upper adhesion layer is provided in the surface in which the polymer film 12 is arrange | positioned with respect to the graphite sheet 11, and the lower adhesion to the surface on the opposite side of the polymer film 12 is carried out. The 2nd adhesion layer 15 as a layer is provided. The thermal diffusion sheet 10 may be attached to the release sheet 16 by the second adhesive layer 15. As an adhesive, since it can apply | coat with thin and uniform thickness, an acrylic adhesive, a urethane type adhesive, a silicone type adhesive, an epoxy clock adhesive, a natural rubber type adhesive etc. are used.

The polymer film 12 has a planar shape that can cover the entire surface of the graphite sheet 11, and the polymer film 12 has a rectangular shape that is slightly larger than the outer shape of the graphite sheet 11. The polymer film 12 sufficiently reinforces the strength of the graphite sheet 11 having brittleness (a phenomenon in which an object hardly exhibits plastic deformation and breaks when subjected to external force), and at the same time, It has a thickness that does not affect heat dissipation. Specifically, the thickness of the polymer film 12 is preferably 18 to 50 μm. When the thickness of the polymer film 12 is more than 50 µm, since heat radiation from the surface of the polymer film 12 becomes difficult, heat generated in the electronic component is accumulated between the graphite sheet 11 and the polymer film 12. On the other hand, when the thickness of the polymer film 12 is less than 18 μm, the strength of the thermal diffusion sheet 10 may not be sufficiently secured. From the viewpoint of having sufficient strength and being relatively easy to obtain, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyethylene (PE) as the material of the polymer film 12 ), Polypropylene (PP), polyimide (PI) and the like are preferably used.

In the center of the polymer film 12, a hole 23 for arranging a square thermally conductive rubber 13 is provided. The hole 23 has a shape substantially the same as that of the thermally conductive rubber 13, and is formed slightly larger than the thermally conductive rubber 13. The thermally conductive rubber 13 is disposed in the hole 23 and is disposed directly on the graphite sheet 11. The thermally conductive rubber 13 is disposed to penetrate the polymer film 12 so as to contact the surface of the graphite sheet 11. In the present embodiment, the thermally conductive rubber 13 is adhered to and fixed to the graphite sheet 11 by the first adhesive layer 14. In addition, the thermally conductive rubber 13 penetrates the first adhesive layer 14 to the surface of the graphite sheet 11 from the viewpoint of facilitating heat dissipation of the heat diffused from the electronic component 1 to the graphite sheet 11. It is preferable that they are directly bonded and fixed.

The thermally conductive rubber 13 includes a thermally conductive filler in the rubber as the base material. The thermally conductive rubber 13 is soft and soft from the viewpoint of enhancing adhesion with a housing close to an electronic component. Soft and soft). From this point of view, besides rubber, organic polymer materials such as gels and lubricants can be used as the base material. However, it is preferable to use elastic bodies, such as rubber | gum, from a viewpoint of shape stability, handling stability, etc. Moreover, from the viewpoint of having high thermal conductivity as the thermally conductive filler, for example, powders of metal oxides, metal nitrides, metal carbides, metal hydroxides, and the like are preferably used. Specifically, aluminum oxide, boron nitride, silicon carbide, aluminum hydroxide And magnesium oxide. The release sheet 17 can be attached to the surface of the thermally conductive rubber 13 in order to prevent surface protection, drying, or the like. The release sheet 17 is made of the same sheet material as the release sheet 16 described above. The thermal diffusion sheet 10 is used so that the release sheets 16 and 17 can be peeled off and then stuck to the surface of the electronic component.

The thermal diffusion sheet 10 is provided with positioning portions 21 and 22, which are two holes, to facilitate positioning with respect to the electronic component. The first positioning portion 21 is provided at the left edge end of the thermal diffusion sheet 10. The first positioning portion 21 is disposed inside the notch 11a and spaced apart from the graphite sheet 11. That is, the 1st positioning part 21 is arrange | positioned in the position which does not overlap with the graphite sheet 11 when viewed from the top. That is, the first positioning portion 21 is a hole penetrating through the polymer film 12 and the first and second adhesive layers 14 and 15.

On the other hand, the second positioning portion 22 is provided near the edge opposite to the first positioning portion 21 with respect to the thermal diffusion sheet 10. The second positioning portion 22 is formed smaller than the square hole 11b of the graphite sheet 11 and is disposed at the same position as the square hole 11b. That is, like the first positioning portion 21, the second positioning portion 22 is disposed at a position not overlapping with the graphite sheet 11 when viewed from above. That is, the second positioning portion 22 is a hole penetrating through the polymer film 12 and the first and second adhesive layers 14 and 15.

As shown in FIGS. 3 and 4, the shape, size, position, and the like of the first and second positioning portions 21 and 22 are engaged by the protrusion structure 4 and 5 disposed in the vicinity of the electronic component 1. It is designed to be. It is preferable to use the thing which heat does not generate | occur | produce as the structures 4 and 5 engaged with both positioning parts 21 and 22, specifically, a screw head etc. are mentioned.

The thermal diffusion sheet 10 is used between the substrate 3 on which the electronic component 1 is mounted and the component 2 such as a housing or a heat sink. That is, the thermal diffusion sheet 10 is used in a state in which the graphite sheet 11 is in close contact with the surface of the electronic component 1 and the thermally conductive rubber 13 is in close contact with the rear surface of the component 2 and compressed in the thickness direction. do. In this state, heat generated from the electronic component 1 is first diffused into the entire graphite sheet 11. The heat is then transferred from the graphite sheet 11 to the component 2 through the thermally conductive rubber 13 and dissipated around the component 2. In this manner, the heat generated from the electronic component 1 continues to dissipate while being diffused into the graphite sheet 11. As a result, temperature rise by heat generated from the electronic component 1 is suppressed.

Next, the method of using the thermal diffusion sheet 10 will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, the peeling sheets 16 and 17 are peeled off from the thermal-diffusion sheet 10 first. Next, the thermal diffusion sheet 10 is disposed on the substrate 3 on which the electronic component 1 is mounted. As shown in FIG. 4, the structure 4 on the substrate 3 is engaged with the first positioning unit 21, and the structure 5 on the substrate 3 is connected to the second positioning unit 22. And the thermal diffusion sheet 10 are pressed against the surface of the electronic component 1. Then, the thermal diffusion sheet 10 is adhered to and fixed to the surface of the electronic component 1 by the second adhesive layer 15. In this manner, the thermal diffusion sheet 10 may be attached at a position where the electronic component 1 is most efficiently radiated. Therefore, the structures 4 and 5 arranged in the vicinity of the electronic component 1 are engaged with both positioning portions 21 and 22, so that the positioning of the thermal diffusion sheet 10 with respect to the electronic component 1 is achieved. It is done easily and surely.

According to this embodiment, the following effects can be acquired.

(1) The thermal diffusion sheet 10 is provided with two positioning portions 21 and 22 which are holes in order to facilitate positioning with respect to the electronic component 1. In this case, the structures 4 and 5 disposed in the vicinity of the electronic component 1 are engaged with both positioning portions 21 and 22, thereby positioning the thermal diffusion sheet 10 with respect to the electronic component 1. It can be performed easily and reliably. Therefore, in the manufacturing process, such as an electronic device, the thermal-diffusion sheet 10 can be attached easily and reliably to the position where the electronic component 1 dissipates most efficiently.

(2) The first and second positioning portions 21 and 22 are both disposed at positions not overlapping with the graphite sheet 11 when viewed from above. That is, the first and second positioning portions 21 and 22 are both holes penetrating through the polymer film 12 and the first and second adhesive layers 14 and 15. In this case, since the graphite sheet 11 is not exposed to both positioning parts 21 and 22, the graphite powder peeled from the graphite sheet 11 can be prevented from scattering. Therefore, it is possible to prevent a problem such as short-circuit of conductor wiring on the substrate 3 caused by the drop of graphite powder.

(3) Both surfaces of the graphite sheet 11, the outer frame, the notches 11a and the inner surfaces of the square holes 11b are covered with an adhesive. In this case, since both surfaces of the graphite sheet 11 are covered by the first and second adhesive layers 14 and 15, it is possible to more reliably prevent the graphite powder peeled from the graphite sheet 11 from scattering.

(4) In the center of the polymer film 12, a hole 23 for arranging the thermally conductive rubber 13 is provided. The thermally conductive rubber 13 is disposed directly on the graphite sheet 11 through the hole 23. That is, the thermally conductive rubber 13 penetrates the polymer film 12 to be in direct contact with the surface of the graphite sheet 11. That is, there is no polymer film 12 between the thermally conductive rubber 13 and the graphite sheet 11. In this case, the heat diffused from the electronic component 1 to the graphite sheet 11 can be radiated around the components 2 such as the housing via the thermal conductive rubber 13. Thereby, it is possible to efficiently dissipate heat while diffusing heat generated from the electronic component 1, and the rise in temperature due to heat generated from the electronic component 1 can be suppressed.

Next, the test for confirming the effect of a thermally conductive rubber is demonstrated concretely. In the test example, a test sample of the thermal diffusion sheet was produced using graphite sheet, PET film and thermally conductive rubber. Specifically, an acrylic pressure-sensitive adhesive was applied to both surfaces of the graphite sheet, a polymer film was attached to one side of the graphite sheet, and then a hole was formed in a predetermined shape, and a thermally conductive rubber was attached to the molded body to prepare a test sample. In the test example, the hole for arranging heat conductive rubber was formed in the center of PET film, and the heat conductive rubber was directly stuck to the graphite sheet through the hole. This test sample was interposed between the housing and the ceramic heater, and the test sample was compressed until its thickness became 0.5 mm. In this case, the test sample was placed between the housing and the ceramic heater by bringing the thermally conductive rubber into close contact with the ceramic heater.

In the comparative example, no hole for arranging the thermally conductive rubber was formed in the PET film. Therefore, the thermally conductive rubber was stuck directly to the polymer film without contacting the graphite sheet. Except this point, the test sample was produced using the manufacturing method similar to a test example. In order to produce each test sample of a test example and a comparative example, the 80-micrometer-thick graphite sheet, the 20-micrometer-thick PET film, and the thermally conductive rubber (10 mm <2>) of 450 micrometers thickness were used. In addition, in each test sample of a test example and a comparative example, the area of the part in which a graphite sheet and a thermally conductive rubber overlap each other was matched.

(Evaluation test regarding thermal characteristics)

About each test sample of a test example and a comparative example, the thermocouple was fixed to the surface of a ceramic heater, and the outer frame of a graphite sheet and a graphite sheet just above a ceramic heater, respectively. Then, the ceramic heater was heated at a voltage of 5 V, and the temperature test of the ceramic heater and the graphite sheet was measured to evaluate the thermal characteristics. In the graph of FIG. 7, two lines A represent a change in temperature of the ceramic heater surface, two lines B represent a change in temperature of the graphite sheet directly above the ceramic heater, and two lines C are in the outer frame of the graphite sheet. Indicates a change in temperature. In addition, the solid line of a line A, B, C shows the temperature change of the test sample of a test example, and the dotted line shows the temperature change of the test sample of a comparative example. Moreover, the thermal resistance and thermal conductivity of each test sample of a test example and a comparative example were calculated | required from said evaluation test, respectively. The thermal resistance is a coefficient representing the difficulty of transferring heat, and the thermal conductivity is a coefficient representing the ease of transferring of heat. The results are shown in Table 1.

Example Comparative example Heat resistance (℃ / W) 2.08 3.15 Thermal Conductivity (W / mK) 2.4 1.6

When the test example was compared with the comparative example from the result of the graph of FIG. 7, it was confirmed that the temperature increase of the surface of the ceramic heater was suppressed. This means that since the thermally conductive rubber can be directly adhered to the graphite sheet, the heat flow from the thermally conductive rubber to the graphite sheet is good, and heat is efficiently radiated from the ceramic heater. On the other hand, in the comparative example, since a polymer film exists between the thermally conductive rubber and the graphite sheet, heat hardly flows from the thermally conductive rubber to the graphite sheet, and heat is not efficiently radiated from the ceramic heater. From the result of Table 1, the test sample of the test example has a lower thermal resistance than the test sample of the comparative example, and the result was high. In addition, in the outer frame of the graphite sheet and the graphite sheet immediately above the ceramic heater, the difference in temperature change between the test example and the comparative example was not seen.

In addition, this embodiment can also be changed as follows and specified.

In this embodiment, the position of the thermal diffusion sheet 10 with respect to the electronic component 1 by engaging the structures 4, 5 on the substrate 3 with the first and second positioning portions 21, 22. Although the determination was made, as shown in FIG. 5, the thermal diffusion sheet 10 was formed by engaging the first and second positioning portions 21 and 22 with the structures 6 and 7 provided in the components 2 such as the housing. It is also possible to perform positioning.

In the present embodiment, the first and second positioning portions are holes, but may be notches.

In the present embodiment, the thermal diffusion sheet 10 includes the polymer film 12 and the thermally conductive rubber 13 on the graphite sheet 11, but the thermally conductive rubber 13 provided in the thermal diffusion sheet as shown in FIG. May be omitted as necessary. The number of the positioning units 21 may be one, three or more.

In the present embodiment, the shapes of the notches 11a and the square holes 11b formed in the graphite sheet 11 may be changed into shapes such as circles, ellipses or semicircles.

1 is a surface view of a thermal diffusion sheet according to the present embodiment.

2 is a cross-sectional view taken along the line 2-2 of FIG.

3 is a cross-sectional view showing a state before pasting a thermal diffusion sheet to an electronic component.

4 is a cross-sectional view showing a state after pasting a thermal diffusion sheet to an electronic component.

5 is a cross-sectional view showing an arrangement structure of a thermal diffusion sheet of another embodiment.

6 is a cross-sectional view showing a thermal diffusion sheet of another embodiment.

7 is a graph showing the results of an evaluation test.

Explanation of the code | symbol described in drawing is as follows.

One… Electronic component (heating element), 3. Substrate, 4 · 5... Structure, 10... Thermal diffusion sheet, 11... Graphite sheet, 12... Polymer film, 11a... Notch, 11b... Square Hall, 14... First adhesive layer (upper adhesive layer), 15... 2nd adhesion layer (lower adhesion layer), 16 * 17 ... Release sheet, 13... Thermally conductive rubber, 21... First positioning portion 22... Second positioning section 23. hole.

Claims (5)

A thermal diffusion sheet comprising a graphite sheet for diffusing heat generated from a heating element and a polymer film provided on the graphite sheet, the thermal diffusion sheet comprising a positioning portion for positioning the heating element. In the thermal diffusion sheet according to claim 1, an upper adhesive layer and a lower adhesive layer are provided on each of the upper and lower surfaces of the graphite sheet, and the polymer film is adhered to the graphite sheet by the upper adhesive layer, and the lower adhesive layer. The thermal diffusion sheet is adhered to the heating element by the thermal diffusion sheet. The heat diffusion sheet according to claim 1 or 2, wherein the positioning portion is a hole penetrating through the polymer film and the upper and lower adhesive layers, and the heating element is disposed on the substrate and positioned on the structure of the protrusion arranged on the substrate. Thermal diffusion sheet, characterized in that the addition. The thermal diffusion sheet according to claim 1 or 2, wherein a thermally conductive rubber is further provided on the graphite sheet, and the polymer film is provided with a hole for disposing the thermally conductive rubber. The positioning method of the thermal diffusion sheet according to claim 1 or 2, wherein the structure arranged near the heating element is engaged with the positioning unit to position the thermal diffusion sheet with respect to the heating element.

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